The present invention relates to a disk cassette containing a disk having information recorded therein.
An information recording medium for a computer, such as a magnetic disk, a magnetooptical disk, an optical disk or the like is accommodated in a disk cassette in consideration of disk protection, etc.
FIG. 1 is an exploded perspective view showing a disk cassette in which a magnetic disc is accommodated.
The disk cassette 10 is fabricated as follows. Prescribed mechanical parts are installed in upper and lower shells 12 and 13 constituting a cassette housing 11 of the disk cassette 10 by a lifter installing process, liners 14 and 15 obtained by perforating unwoven cloth in a circular shape are attached to the shells 12 and 13 by a liner installing process, and then a disk 16 which is completed through a sheet fabricating process is sandwiched between the upper and lower shells 12 and 13 through the liners 14 and 15 by a write protector installing process and a disk installing process. Thereafter, the upper and lower shells 12 and 13 are fused and integrated into the cassette housing 11 by an ultrasonic welding process, and a shutter 17 is secured through a shutter spring 18 to the cassette housing 11 so as to be slidable in parallel to the side surfaces of the cassette housing 11 and open/close a head insertion hole 11a formed in the cassette housing 11.
The shutter spring 18 is a torsion spring serving as urging means which urges the shutter 17 to perform an open/close operation. The shutter spring 18 is hooked to the cassette housing 11 at one end of one arm thereof while hooked to the shutter 17 at one end of the other arm thereof, whereby it urges the shutter 17 so as to close the head insertion hole 11a.
When the shutter 17 and the shutter spring 18 are installed into the cassette housing 11, the shutter 17 is first mounted on the outside surfaces of the cassette housing 11, and then the shutter spring 18 is inserted into the cassette housing 11 from a shutter spring insertion groove 11b provided to the cassette housing 11 and secured to the cassette housing 11.
That is, as shown in FIG. 3A, after the shutter 17 is inserted into the cassette housing 11, the shutter spring 18 is moved in a direction as indicated by an arrow a while one end of one arm portion 18a of the shutter spring 18 is held by an insertion jig, and one end of the other arm portion 18b of the shutter spring 18 is inserted from the shutter spring insertion groove 11b along a spring guide notched portion 12a into the cassette housing 11 and hooked thereto.
Subsequently, as shown in FIG. 3B, one arm portion 18a of the shutter spring 18 is pushed in a direction as indicated by an arrow b to insert the shutter spring 18 from the shutter spring groove 11b into the cassette housing 11. At this time, as shown in FIG. 3C, one end of one arm portion 18a of the shutter spring 18 is detached from the insertion jig, opened in a direction as indicated by an arrow c, and then hooked to a spring hook portion 17a, thereby completing the installing process.
When the disk cassette 10 thus constructed is in nonuse, the head insertion hole 11a is closed by the shutter 17 to protect the disk 16. On the other hand, when the disk cassette 10 is in use, the head insertion hole 11a is opened by the shutter 17 to partially expose the disk 16 and record/reproduce information in/from the disk 16.
Following the recent enhancement in recording density of disks as described above, it becomes more important to enhance hermeticity and rigidity of disk cassettes for the purpose of high-precision information recording/reproduction for disks and stable running of the disks. However, a portion of the shutter spring insertion groove 11b of the conventional disk cassette 10 which is not covered by the shutter 17 is open, and thus the hermeticity of the disk cassette 10 is reduced. As a result, there is a problem that dust invades into the cassette housing 11.
Further, the shutter spring insertion groove 11b is formed at the substantially same length as one side of the cassette housing 11. Therefore, the thickness of the cassette housing 11 at that portion is smaller, and the rigidity of the disk cassette 10 is reduced. As a result, there are problems that the cassette housing 11 is distorted, resulting in disturbance of stable running of the disk 16, and that the shutter 17 falls out when the disk cassette 10 falls down by mistake.